Early humans in eastern Africa crafted advanced tools and displayed
other complex behaviors tens of thousands of years earlier than
previously thought, according to a trio of papers published on 15
March in Science. 1,2,3

Those advances coincided
with - and may have been driven by - major climate and landscape
changes.

The latest evidence comes from the
Olorgesailie Basin in Southern
Kenya, where researchers have previously found traces of ancient
relatives of modern human as far back as 1.2 million years ago.

Evidence collected at
sites in the basin suggests that early humans underwent a series of
profound changes at some point before roughly 320,000 years ago.
They abandoned simple hand axes in favor of smaller and more
advanced blades made from obsidian and other materials obtained from
distant sources.

That shift suggests the
early people living there had developed a trade network - evidence
of growing sophistication in behavior.

The researchers also
found gouges on black and red rocks and minerals, which indicate
that early Olorgesailie residents used those materials to create
pigments and possibly communicate ideas.

These changes occurred at the same time as larger animals
disappeared from the site and were replaced by smaller creatures.

"It's a one-two punch combining tectonic shifts and climate shifts,"
says Rick Potts, who led the work as director of the human origins program at the Smithsonian Institution in Washington DC.

"That's the
kind of stuff out of which evolution arises."

Researchers from the Smithsonian Institution and their colleagues

tracked changes in the behavior of
early humans in Kenya's Olorgesailie Basin.

Credit: Human Origins Program,
Smithsonian

The studies push
back the timeline for such behavior by around 100,000 years, adding
to a growing body of evidence suggesting that the roots of human
culture are deeper and more extensive than once thought.

The latest evidence
is,

"probably not enough to put the question to rest as to what
effect the climate variability had on human behavior", says Nick Blegen, an anthropologist at the Max Planck Institute for the
Science of Human History in Jena, Germany.

Researchers have
traditionally thought that H. sapiens emerged around 200,000
years ago, but
fossils discovered in Moroccocould push that date to more than
300,000 years ago. 4

Nick Blegen has
documented the transport of obsidian in central Kenya roughly
200,000 years ago,5 and he is preparing another study
that would push that record back to 396,000 years ago at the same
site.

The
record for such complex behavior is likely to extend back even
further, he says, but it is not clear whether the environment is
shaping human behavior, or whether advances in human behavior are
enabling them to inhabit riskier environments.﻿

Complex tools

Excavations in the
Olorgesailie Basin have been turning up Stone Age artifacts ever
since
Louis and Mary Leakey pioneered work there in
the 1940s.

But this is the
first time that scientists have documented evidence of more advanced
tools and behaviors typically associated with the Middle Stone Age,
which lasted until 25,000-50,000 years ago, says Alison Brooks,
an anthropologist at George Washington University in Washington DC,
who led the dating and analysis of the latest artifacts.

Isotopic dating
techniques helped the team to pin down the age of the stone
tools, and the researchers traced the obsidian back to its
sources, which were mostly located 25-50 kilometers away in
multiple directions.

"It's the
best evidence yet for the exchange of raw materials" so
early in time, Brooks says.

Curtis
Marean, a paleoanthropologist at the University of Arizona
in Tempe, says he isn't yet convinced by the evidence for trade.

"To
demonstrate extended social networks, I would like to see
regular and systematic transport of raw material across a
number of artifact types on the order of 100 kilometers," he
says.

The team cannot
say exactly how long before 320,000 years these changes happened
because an extended period of erosion at the site wiped out the
archaeological record there between 499,000 and 320,000 years
ago.

Some
information could come from several projects that drilled into
ancient lake beds in Kenya and Ethiopia to collect a detailed
record of environmental and ecological changes in the region.
6

Rick
Potts and his
team drilled two of those cores in the southern Olorgaseilie
Basin, and
Potts says the cores
cover the entire period that is missing from the archaeological
record.

Comparisons
with cores drilled elsewhere in East Africa should help
scientists to differentiate between events happening locally and
broader regional climatic trends.

"The drill
cores I hope will be a game changer, because of the
precision of the environmental record and hopefully the
precision of the dating," Potts says.

Then it's a
matter of working to understand how animals and people might
have responded to the changing environment, Potts says.

"Only then
can we say anything about how climate is really affecting
human evolution."